Thursday, February 18, 2010

Voles' Holes

Days are getting longer, the snow cover is receding, and look what it exposed all around the base of the bird feeding station!

They circle the area!

And in front of each hole, there is a pile of empty sunflower seed shells.

A little closer view!  Regretfully, I was never quite quick enough to capture any of the voles as they darted in and out of the safety of their little holes. 
Here in New England, voles, mice, and shrews live in and navigate through tunnels under the snow cover.  This area is called the "subnivian space", an extensive, continuous air space at ground level between the snow and the earth.  Temperatures maintain a fairly even 32 degrees F.

In Bernd Heinrich's book, Winter World,  he explains that near the top of any snowpack, the snow gets denser as the crystals bond together.  But, closer to the ground, where it is warmer than at the surface, water vapor from disintergrating snow crystals migrates upward and recondenses, freezing onto the upper snow pack crystals, and creating this subnivian space.

Young trees are very susceptible to the hungry winter appetites of these little critters.  They will chew the young, tender bark right off the bottom of the trunks, all the way up to the top of the snow mark.  It is enough to damage and kill the tree.  Trees planted purposefully will require protection!

Here's a picture of a picture sketched by Bernd to illustrate the activity described above.
Note the grass nest to the left.  Mice, voles, and shrews will breed very early in the spring when the sun is bright enough to penetrate the frozen ice crystals overhead.  Voles, especially, are very prolific!
But with the help of owls, foxes, coyotes, and weasels, their population remains manageable.
Great grey owls can hear the movement clear through the snow cover from 30 meters away (that's well over 90 feet!), and using their balled up feet, will crash right through the snow to catch their prey. Foxes and coyotes located voles by sound, as well, and dig through the snow for their tasty treat.

One final, interesting note - when the snow cover totally recedes and the voles vacate their fully exposed grass nests, they are often taken over by bumblebee queens that are starting new colonies.

There is just so much going on in our natural world.  How could one not be curious?

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Lily Hydrangea said...

I've never heard of a Vole. I love how you see evidence of their activities around the openings of the tunnels.

Tozz said...

I loved reading about the little mice and voles. I have never heard of this happening and its amazing what goes on in the world with nature :)

This Is My Blog - fishing guy said...

Karen: That is so interesting. I've never seen them around Ohio and also never seen the holes in the snow.

MyMaracas said...

Subnivia ... sounds like a fantasy world, doesn't it? This was a really interesting and informative post. I've never seen holes like that in the snow melt, but I'll watch for them - if the snow ever melts here.

Stephanie said...

My dear Abby sniffs them out buries her head in the snow, digs a big and has a snack. Poor voles.

KaHolly said...

Lily, a vole is like a mouse, only different. They are sometimes called field mice. I went back and put a link in the post.

Tozz, thanks so much for stopping by today! I enjoy your blog so much. I'll be back to sewing soon!

FG, They're pretty secretive little fellows, but you've got them in Ohio!!

MM, it DOES sound like something out of a Terry Brooks book, doesn't it? I hadn't thought about that. I like it!! Thanks for the visit! ~karen

Judy said...

So that is why the snow gets easier to walk on, the longer it lies on the ground! And subnivia is such a neat word!

Anonymous said...

Great post, I really enjoyed reading about the snow tunnels!
And thanks for visiting my blog and leaving your nice comment!

Anonymous said...

When we lived in winthrop, WA we saw this too and actually could then see the voles feeding below the feeders. They were actually quite tame for us to come near to them. They were certainly a pleasurable surprise to us too.

eileeninmd said...

How cool, I have noticed some holes too and wondered what kind of critter was there.

The Early Birder said...

Super and informative post Karen. Have a good weekend...FAB.

John said...

Wonderful post Karen, the little holes in the Snow would have me captivated and would want to find out more, like fixing remote cameras to capture them when they came out...

Keep us posted.


Carver said...

I enjoyed this post. I've seen voles but never caught a shot of them. I think capturing the vole holes in the snow is fantastic.

ramblingwoods said...

Ah..I love that book and he has a new one out for the summer. I have many of his books. Love him. Well you had me looking for vole activity in the yard. I found a bled out one back a while ago and I think someone must have poison out which is scary as something could have eaten this little vole.. Welcome to Nature Notes.. I am happy to have you... Michelle

Martha Miller said...

Hi Karen!

I sent this link to my 9 year old grandson. He is working on a project about white footed mice, and spent a good chunk of time yesterday looking all around the woods in the snow for some signs of them! I always love your pics!

Stine in Ontario said...

Aren't voles clever?

Patty L said...

Wow! Your posts are popular!! and very well done I might add... I learned a thing or tow even after having had a conversation with you about this very subject!!
Keep up the good work!! But no pressure... settle in up north and we'll hear from you soon enough... gotta check out that email blog alert thing you mentioned!
Hugs, P-

Anonymous said...

That's fascinating. I had no idea all that was going on under the surface of the snow,though I did know that the owls and others would locate small prey by sound beneath the snow.

Marvin said...

Thank you for the very informative post. Our plastic covered fall garden bed became a much used vole retreat in late fall. It provided warmth, food and protection from most predators. What more could a vole want?

Mary said...

How interesting! I've heard of voles, but never knew they did this and would not have known the holes in the snow were from them.